Frenkel defect process in amorphous silica

2011 ◽  
Author(s):  
Koichi Kajihara ◽  
Masahiro Hirano ◽  
Linards Skuja ◽  
Hideo Hosono
Keyword(s):  
Amorphous Silica ◽  
Frenkel Defect ◽  
Defect Process

Amorphous silica coating on α-alumina particles

1995 ◽  
Vol 53 ◽  
pp. 210-211
Author(s):  
J. W. Mellowes ◽  
C. M. Chun ◽  
I. A. Aksay
Keyword(s):  
Amorphous Silica ◽  
Heterogeneous Nucleation ◽  
Homogeneous Nucleation ◽  
Silica Coating ◽  
Full Density ◽  
Optimal Conditions ◽  
Fine Grained ◽  
Alumina Particles ◽  
Complete Mullitization ◽  
Powder Compacts

Mullite (3Al2O32SiO2) can be fabricated by transient viscous sintering using composite particles which consist of inner cores of a-alumina and outer coatings of amorphous silica. Powder compacts prepared with these particles are sintered to almost full density at relatively low temperatures (~1300°C) and converted to dense, fine-grained mullite at higher temperatures (>1500°C) by reaction between the alumina core and the silica coating. In order to achieve complete mullitization, optimal conditions for coating alumina particles with amorphous silica must be achieved. Formation of amorphous silica can occur in solution (homogeneous nucleation) or on the surface of alumina (heterogeneous nucleation) depending on the degree of supersaturation of the solvent in which the particles are immersed. Successful coating of silica on alumina occurs when heterogeneous nucleation is promoted and homogeneous nucleation is suppressed. Therefore, one key to successful coating is an understanding of the factors such as pH and concentration that control silica nucleation in aqueous solutions. In the current work, we use TEM to determine the optimal conditions of this processing.

Mechanoactivation Of Rice Husk Ash In Laboratory Conditions

2019 ◽  
pp. 20-26
Keyword(s):  
Mechanical Activation ◽  
Rice Husk ◽  
Amorphous Silica ◽  
Silicon Oxide ◽  
Rice Husk Ash ◽  
Pozzolanic Activity ◽  
Maximum Solubility ◽  
Laboratory Conditions ◽  
Before And After ◽  
Mineral Additive

In many rice producing countries of the world, including in Vietnam, various research aimed at using rice husk ash (RHA) as a finely dispersed active mineral additive in cements, concrete and mortars are being conducted. The effect of the duration of the mechanoactivation of the RHA, produced under laboratory conditions in Vietnam, on its pozzolanic activity were investigated in this study. The composition of ash was investigated by laser granulometry and the values of indicators characterizing the dispersion of its particles before and after mechanical activation were established. The content of soluble amorphous silicon oxide in rice husk ash samples was determined by photocolorimetric analysis. The pizzolanic activity of the RHA, fly ash and the silica fume was also compared according to the method of absorption of the solution of the active mineral additive. It is established that the duration of the mechanical activation of rice husk ash by grinding in a vibratory mill is optimal for increasing its pozzolanic activity, since it simultaneously results in the production of the most dispersed ash particles with the highest specific surface area and maximum solubility of the amorphous silica contained in it. Longer grinding does not lead to further reduction in the size of ash particles, which can be explained by their aggregation, and also reduces the solubility of amorphous silica in an aqueous alkaline medium.

scholarly journals Simultaneous amorphous silica and phosphorus recovery from rice husk poultry litter ash

RSC Advances ◽  
2021 ◽  
Vol 11 (15) ◽  
pp. 8927-8939
Author(s):  
Laura Fiameni ◽  
Ahmad Assi ◽  
Ario Fahimi ◽  
Bruno Valentim ◽  
Karen Moreira ◽  
...  
Keyword(s):  
Rice Husk ◽  
Amorphous Silica ◽  
Poultry Litter ◽  
Phosphorus Recovery ◽  
Secondary Source ◽  
Poultry Litter Ash

Rice husk poultry litter ash (RHPLA) is proposed as a valuable secondary source to recover phopshorus and amorphous silica in three steps.

Complex Formation and Dissociation Dynamics on Amorphous Silica Surfaces

2021 ◽  
Author(s):  
Steven A. Yamada ◽  
Samantha T. Hung ◽  
Jae Yoon Shin ◽  
Michael D. Fayer
Keyword(s):  
Complex Formation ◽  
Amorphous Silica ◽  
Silica Surfaces ◽  
Dissociation Dynamics
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